The invention relates to an apparatus for the continuous electrolytic extraction of metals from a metal ion solution in which an anode and a cathode, both electrically connected to a power supply, are immersed. The cathode has a surface configured as a continuous flexible band partly immersed in the solution and passing through it. The deposited metal is removed from this surface outside the solution. The flexible band is metallic at least on the one part of its surface on which the metal is deposited. A scraper for the removal of the deposited metal is disposed outside the solution, and the band is guided by means of guiding and driving rollers.
U.S. Pat. No. 4,786,384 discloses an electrolytic cell for the electrolytic extraction of metals from a liquid containing metal ions, particularly process waste water. In a trough, this cell contains a multiple of planar electrodes spaced apart in parallel. The cathodes have openings and are connected to the power source via differently sized connecting resistors, depending on the distance to the anode, such that the same current density is supplied to each cathode.
The problems involved in the operation of such an apparatus include the individual withdrawal of the cathode surface bearing the deposited metal, which involves excessive labor costs and the relatively labor-energy-intensive removal of the deposited material.
U.S. Pat. No. 4,647,345 discloses an electrolytic apparatus for the continuous manufacture of metal foils from a solution which contains metal ions and is stored in a tank. The cathode which is partly immersed in the solution is configured as a drum or a continuously moving band. In the immersed area, it is surrounded by a spaced apart anode which is provided with channels and openings for the supply of electrolyte. After the withdrawal from the solution, the metal, which is deposited on the cathode, is separated from the cathode.
The cathode has a surface consisting of metal, for example, titanium or tantalum, whereas the anode is made of titanium, for example. The solution used is an acidic metal ion solution, for example, copper sulfate or sulfuric acid.
One problem is the continuous extraction of metals by means of a movable cathode unless it is possible to deposit homogeneous compact self-supporting metal layers on the cathode. This is particularly difficult in case of slurry-like metal structures or dendrites or other non defined metal structures, like spherical structures which do not form homogeneous layers among each other during precipitation.
Further, U.S. Pat. No. 2,099,873 discloses an apparatus for extracting flocculent material from an electrolytic bath where the cathode is also a moving, continuous flexible band. The metal (chromium) is cathodically deposited on the band and from the electrolytic solution, it is supplied to separate a rinsing device where the deposited metal (chromium) is separated from the band. The band is guided by means of guiding and driving rollers. One driving roller guiding the band is rotated with its axis horizontally disposed above the bath. Only a minor portion of the surface area of the roller, which is large in comparison to the tank, immerses in the bath. A plurality of guiding rollers is provided outside the bath.
U.S. Pat. No. 2,748,071 discloses an apparatus for the regeneration of iron chloride in a copper etching process where a cathode surface which is also configured as a continuous band is guided via guiding and driving rollers. After emerging from the solution, the band is fed to a water bath in order to separate the copper. The scraper is a surgical knife, and the metal (copper) is supplied to another electrolytic tank. A removal of dried, powderized metal is not intended.
U.S. Pat. No. 2,964,453 also describes a regeneration process for a copper etching bath where a flexible band (platinum) is used which successively passes an etching bath, a rinsing bath and scraping bath. In the etching bath, the band operates cathodically and in the scraping bath anodically. The publication does not mention a mechanical scraping device as required in the practice to continue the processing of dried deposited material.
U.S. Pat. No. 2,985,568 discloses an electrolytic process for producing organometallic compounds which also features a metallic continuous band. A problem in this apparatus is the sealing of the hub of the cathode drum and the power supply to the cathode drum inside the electrolyte. Outside the bath, the continuous band passes a station with a mechanical scraper in the form of a knife.